Typical multi-pole circuit breakers have a common cross bar member for operation of all poles of a multi-pole circuit breaker simultaneously. Typical circuit breakers of the type contemplated herein are shown and described in U.S. Pat. No. 4,594,567, entitled "Circuit Breaker Contact Arm Assembly Having A Magnetic Carrier," issued on Jun. 10, 1986; U.S. Pat. No. 4,680,564, entitled "Multi-Pole Molded Case Circuit Breaker With A Common Contact Operating Crossbar Member," issued on Jul. 14, 1987, and U.S. Pat. No. 4,595,896, entitled "Molded Case Circuit Breaker Having A Reinforced Housing," issued on Jun. 17, 1986, each of which has a fixed load contact arm.
A dual movable contact circuit breaker is shown and described in U.S. Pat. No. 5,184,099, entitled "Circuit Breaker With Dual Movable Contacts," issued on Feb. 2, 1993, which includes a pivotally semi-stationary load contact arm and line contact arm. The load contact arm is semi-stationary because it only moves under high current blow-apart conditions. The load contact arm and line contact arm separate in response to a high level current sufficient to blow the arms apart. The load contact arm is subjected to a reduced upward force after the arm has moved downward from its operating position. This is achieved by an arrangement which includes a set of springs which bias the load contact arm toward its operating position with the different levels of force. The first level of force is greater than the second level of force, and holds the load contact arm in its operating position against the downward force applied through the contacts from the line contact arm to the load contact arm. The second level of force allows the load contact arm to move downward with reduced force when the arms blow apart due to electromagnetic forces. A U-shaped housing magnetically attracts the line contact arm to allow the arms to blow apart more swiftly and to prevent the return of the load contact arm to its operating position until the arc between the arms is extinguished.
While various arrangements are available to provide variable or multi-level support force to contact support arms, it is important to configure such supports to function properly within the associated circuit breaker. Thus, due to the very high competition in the circuit breaker market, it would be desirable to provide a contact arm support device with multi-level support forces, improved performance characteristics and reduced cost.